The invention pertains to a pneumatically powered turbine which comprises a turbine wheel with a peripheral row of blades, and a stator housing having one or more nozzles for directing motive air at high speed onto said blades to rotate said turbine wheel, and an air outlet located substantially opposite said nozzle or nozzles in the axial direction and downstream of the turbine wheel.
A problem inherent in turbines of the above type relates to mechanical blade wear due to hard particles bouncing between the stator housing inner wall and the blades without being able to pass the blades and reach the outlet. This is a problem particularly with smaller turbines where realtively soft materials are used for the turbine wheel and the blades, e.g. aluminum alloy or plastics. Due to a very high peripheral velocity, particles that may have gotten into the turbine through the air inlet during operation or which may have been "installed" in the turbine at the assembly of the turbine cause very rapidly deformations of the blades. The result is an impaired efficiency of the turbine and a shortened service life.